Semiconductor device and method for manufacturing the same

Abstract

An object is to manufacture a semiconductor device with high reliability by providing the semiconductor device including an oxide semiconductor with stable electric characteristics. In a transistor including an oxide semiconductor layer, a gallium oxide film is used for a gate insulating layer and made in contact with an oxide semiconductor layer. Further, gallium oxide films are provided so as to sandwich the oxide semiconductor layer, whereby reliability is increased. Furthermore, the gate insulating layer may have a stacked structure of a gallium oxide film and a hafnium oxide film.

What is claimed is: 
     
       1. A semiconductor device comprising:
 a first gate electrode over a substrate; 
 a first metal oxide film over the first gate electrode; 
 an oxide semiconductor layer over the first metal oxide film; 
 a source electrode and a drain electrode electrically connected to the oxide semiconductor layer; 
 a second metal oxide film over the oxide semiconductor layer, the source electrode, and the drain electrode; and 
 a second gate electrode over the second metal oxide film, 
 wherein the first metal oxide film and the second metal oxide film each comprises a film containing gallium. 
 
     
     
       2. The semiconductor device according to  claim 1 , wherein the first metal oxide film and the second metal oxide film are each an insulating film. 
     
     
       3. The semiconductor device according to  claim 1 , wherein the second gate electrode does not overlap with the source electrode and the drain electrode. 
     
     
       4. The semiconductor device according to  claim 1 , wherein the oxide semiconductor layer contains at least gallium. 
     
     
       5. The semiconductor device according to  claim 1 , wherein the oxide semiconductor layer contains indium, zinc and a metal other than indium and zinc. 
     
     
       6. The semiconductor device according to  claim 1 ,
 wherein the first metal oxide film and the second metal oxide film are each formed of a stacked structure including the film containing gallium and a film containing hafnium, and 
 wherein the films containing gallium are each in contact with the oxide semiconductor layer. 
 
     
     
       7. The semiconductor device according to  claim 6 , wherein the film containing hafnium is one selected from the group consisting of a hafnium oxide film, a hafnium silicate film, a hafnium oxynitride silicate film, and a hafnium aluminate film. 
     
     
       8. The semiconductor device according to  claim 1 , wherein the first metal oxide film and the second oxide film are each a gallium oxide film. 
     
     
       9. A semiconductor device comprising:
 a first metal oxide film over a substrate; 
 an oxide semiconductor layer over the first metal oxide film; 
 a source electrode and a drain electrode electrically connected to the oxide semiconductor layer; 
 a second metal oxide film over the oxide semiconductor layer, the source electrode, and the drain electrode; and 
 a gate electrode over the second metal oxide film, 
 wherein the first metal oxide film and the second metal oxide film each comprises a film containing gallium. 
 
     
     
       10. The semiconductor device according to  claim 9 , wherein the first metal oxide film and the second metal oxide film are each an insulating film. 
     
     
       11. The semiconductor device according to  claim 9 , wherein the gate electrode does not overlap with the source electrode and the drain electrode. 
     
     
       12. The semiconductor device according to  claim 9 , wherein the oxide semiconductor layer contains at least gallium. 
     
     
       13. The semiconductor device according to  claim 9 , wherein the oxide semiconductor layer contains indium, zinc and a metal other than indium and zinc. 
     
     
       14. The semiconductor device according to  claim 9 ,
 wherein the first metal oxide film and the second metal oxide film are each formed of a stacked structure including the film containing gallium and a film containing hafnium, and 
 wherein the films containing gallium are each in contact with the oxide semiconductor layer. 
 
     
     
       15. The semiconductor device according to  claim 14 , wherein the film containing hafnium is one selected from the group consisting of a hafnium oxide film, a hafnium silicate film, a hafnium oxynitride silicate film, and a hafnium aluminate film. 
     
     
       16. The semiconductor device according to  claim 9 , wherein at least one of the first metal oxide film and the second metal oxide film is a gallium oxide film. 
     
     
       17. A semiconductor device comprising:
 a gate electrode over a substrate; 
 a first metal oxide film over the gate electrode; 
 an oxide semiconductor layer over the first metal oxide film; 
 a source electrode and a drain electrode electrically connected to the oxide semiconductor layer; and 
 a second metal oxide film over the oxide semiconductor layer, the source electrode, and the drain electrode, 
 wherein the first metal oxide film and the second metal oxide film each comprises a film containing gallium, and 
 wherein the first metal oxide film is formed of a stacked structure including the film containing gallium and a film containing hafnium, and the film containing gallium is in contact with the oxide semiconductor layer. 
 
     
     
       18. The semiconductor device according to  claim 17 , wherein the first metal oxide film and the second metal oxide film are each an insulating film. 
     
     
       19. The semiconductor device according to  claim 17 , wherein the oxide semiconductor layer contains at least gallium. 
     
     
       20. The semiconductor device according to  claim 17 , wherein the oxide semiconductor layer contains indium, zinc and a metal other than indium and zinc. 
     
     
       21. The semiconductor device according to  claim 17 ,
 wherein the second metal oxide film is formed of a stacked structure including the film containing gallium and a film containing hafnium, and 
 wherein the film containing gallium is in contact with the oxide semiconductor layer. 
 
     
     
       22. The semiconductor device according to  claim 17 , wherein the film containing hafnium is one selected from the group consisting of a hafnium oxide film, a hafnium silicate film, a hafnium oxynitride silicate film, and a hafnium aluminate film.